Lightening the load

Grids look to store energy

Large-scale battery storage is set to become an integral part of power grids around the world. This is partly because diversification of power generation from traditional thermal plants to newer and more varied forms, such as renewables and continental interconnectors, makes managing the grid more complex.

Using batteries to manage renewables is important, but the need to apply the technology to balance out the daily load cycle is arguably greater. If you look at the UK’s load curve through the day, there is a peak in the late afternoon between 4pm and 7pm. A consistent daily peak is a pattern repeated around the world (although the time varies). Currently the variation in load up to peak is about four times greater than the variation in the supply from renewables. It matters because the peak evening load dictates how many generators are needed on the network, which dictates the size of both the transmission and distribution systems.

Effectively, says Douglas Ramsay, an electrical engineer in Mott MacDonald’s transmission and distribution team, the sector is using capital expenditure to provide for this three-hour peak. “Frequency control is the need to balance supply and demand on a second-by-second basis,” he explains. “When the load in the network goes down, you have to pull back the generation, and when the load goes up, you have to add some extra generation”.

Big batteries, delivering tens of megawatts of power, could increase the network’s capability to deal with a large and sudden variation in generation and load, while also storing enough power to serve peak demand periods. This has huge potential benefits for the network.

The economics of battery storage are beginning to stack up. The price of batteries has been falling by around 15% a year, and has halved over the past five years. And it seems that a tipping point has been reached in the past 12 months. As projects become economic, the move to battery storage is accelerating. As Douglas puts it: “We are starting to see things happening now that were considered science fiction five years ago”. He believes that using battery storage to help manage supply and demand is about to become a huge market.

There is already strong evidence the supply stream is ramping up to meet the expected demand. Tesla’s Gigafactory, a lithium-ion battery factory in the Nevada desert near Reno, opened in July 2016 and will reach full output in 2022. Battery producing factories are planned around the world by other manufacturers.

The case for battery storage

It’s not only the world’s grid operators that can benefit from battery storage. Take a water company that requires more power. It would likely be charged a significant amount by the local distribution network operator to install an extra connection. Installing a battery would not only potentially remove the need for a new connection, it would save the company money by enabling it to avoid drawing power from the grid when the highest tariffs apply. “That’s a real motivation,” says Douglas. “Loping off your peak load means you pay less for your current electricity, but you can also earn money because batteries help match generation and load across the grid and there are big incentives in place to do that”.

He believes this could have a big impact on the types of projects the Mott MacDonald transmission and distribution team gets involved with in the future. Traditionally clients have operated on a national scale and the work tended to be “huge chunky projects in the power sector”.

Although large-scale battery storage will be associated with big power projects, Douglas says the technology also has clear benefits for other development schemes that require large power loads. “In the future we will need to get involved with companies working on airports and waterworks, and designing datacentres, and help them build large batteries into their projects,” he says.